Hardenable compositions comprising polyacid(s) and polyol(s)

ABSTRACT

The present invention provides hardenable coating compositions, comprising: a first compound selected from the group consisting of polyacids, polyanhydrides, salts thereof and mixtures thereof, and a second compound having two or more active hydrogen groups. When used as a roll coating composition, the first compound preferably has a low average molecular weight and an acid number greater than about 100. The hardenable coating composition preferably has an extended open time and can be rapidly cured to a substantially tack-free state in less than about one minute at 200° C. Coated articles and methods of coating are also provided.

RELATED APPLICATIONS

This application is a National Stage application of under 35 U.S.C. §371and claims benefit under 35 U.S.C. §119(a) of the InternationalApplication No. PCT/US01/21748 having an International filing date ofJul. 11, 2001, which claims the benefit of U.S. Provisional ApplicationNo. 60/218,592, filed on Jul. 17, 2000 each of which is herebyincorporated in its entirety.

BACKGROUND

Painted metal containers (e.g., steel or aluminum cans) are now usedprolifically for packaging foods and beverages. To that end, in 1999,one corporation manufactured over 37 billion aluminum cans for theUnited States beverage industry alone. Metal containers such as aluminumcans may be painted, e.g., by rolling individual cans againstpaint-covered rubber cylinders. Often a clear protective coating isapplied to protect this exterior paint coat from smearing, marring, ordegradation. Cans are then conveyed through ovens for curing and dryingof the coating.

Investigators continue to search for new coating compositions that canbe used in container mass production applications. One goal is todevelop coating compositions that are ready for immediate use withoutadditional preparation steps (i.e., that are “one-stage”). Thecompositions of interest must be stable in bulk quantities at standardtemperature and pressure so that they may be efficiently and costeffectively shipped and stored without gellation or degradation prior touse. They also must be able to withstand the conditions of processing.When applied to substrates, the compositions must cure and dry rapidly(i.e., possess “snap cure” capabilities), have good adhesion to metaland other materials, be scratch resistant, and have a clear and glossyappearance.

New exterior coating compositions that meet these requirements are beingdeveloped. Many of these coatings, however, are variants of formulationsemployed traditionally in the packaging industry, includingphenol/formaldehyde, urea/formaldehyde, and melamine/formaldehydeformulations. However, the widespread use of formaldehyde in productionscale applications is falling into disfavor because of perceivedenvironmental and health considerations. Formaldehyde is an eye and skinirritant that is a suspected carcinogen. The unfavorable environmentaland toxicological profiles of formaldehyde have spurred researchers todevelop new coating formulations that contain formaldehyde scavengers.Unfortunately, such coatings have many shortcomings. For example, resinscontaining formaldehyde scavengers such as melamine, urea, or ammonia,frequently have low water tolerance and require the need for stabilizingemulsifiers. Rogue formaldehyde emissions, as well as additional,stability-related problems associated with heating and curingoperations, also pose complications.

In addition to the environmental concerns about formaldehyde, there isadditional interest in reducing the levels of volatile organic compounds(VOCs) in industrial products such as coating compositions. Thisinterest is in part due to governmental regulations limiting theindustrial use of and the resulting emissions of these into theatmosphere. Consequently, many of the coating compositions presentlyavailable do not meet the new regulations.

As a result, there is a need in the packaging industry for substantiallyformaldehyde-free hardenable compositions that are easy to use. There isalso a need for compositions that exhibit favorable crosslinking andcoating characteristics. In particular, there is a need to developcoating compositions and formulations that are stable at standardtemperature and pressure (i.e., 25° C. and 1 atmosphere) so that theycan be transported and stored in bulk prior to use in production scaleoperations. There is also a need for coating compositions andformulations that have stability and curing profiles that comport withproduction scale applications and are snap-curable, that adhere tosubstrates such as metal, that have a clear, glossy appearance, and thatare mar resistant.

It also would be useful to prepare formaldehyde-free roll coatingcompositions that are non-misting. The coating compositions of thepresent invention solve these and other problems.

SUMMARY

The present invention relates generally to hardenable or curablecompositions (e.g., coating compositions suitable for coating substratessuch as metal cans).

Preferred compositions of the present invention incorporate (i) a firstcompound selected from the group consisting of polyacids,polyanhydrides, salts thereof and mixtures thereof, having an acidnumber greater than about 100, and (ii) a second compound having two ormore active hydrogen groups.

When used in roll coating operations these preferred compositions haveextended pen time. While not intending to be bound by theory, it isbelieved that open time is extended when compositions are capable ofreadily re-dissolving with an additional application of the composition.For example, a composition might be prevented from drying out on acoating roll if it readily re-dissolves into “wet” composition thatcontacts the roll.

Preferred compositions cure and dry rapidly (i.e., possess “snap cure”capabilities), have good adhesion to metal and other materials, arescratch resistant, and have a clear and glossy appearance. Preferredroll coating compositions are also no more than slightly misting andmore preferably are non-misting.

DEFINITIONS

The terms related to hardenable compositions and methods for coatingsubstrates are used in accordance with the understanding of one skilledin the art, unless otherwise noted. For example, as used herein:

The terms “solids content”; “percent solids”; “coating solids” and“coating solids component” refer to the sum of the mass of componentsused in the composition exclusive of water or organic solvent as apercentage of the total composition mass inclusive of any water ororganic solvent.

The term “extended open time” refers to the time that a roll coatingcomposition can be used continuously on an open roll coater withoutbecoming hardened on the roll and causing coating problems such asstreaks, etc. Extended open time may be assessed for a roll coatingcomposition by performing an air-drying test. This test, as describedherein, measures the ability of a liquid coating, applied to yield a dryfilm thickness of 2.2+/−0.63 g/m², to remain tacky at room temperature(25° C.). Preferred coatings remain tacky for at least 15 minutes atroom temperature, more preferred coatings remain tacky for at least 30minutes at room temperature, and most preferred coatings remain tackyfor at least one hour at room temperature.

The term “substantially formaldehyde-free” means that the compositionsof the present invention are contaminated with, or liberate as a resultof curing, no more than about 1 percent by weight formaldehyde. The term“essentially formaldehyde-free” means that the compositions of thepresent invention are contaminated with, or liberate as a result ofcuring, no more than about 0.5 percent by weight formaldehyde. The term“essentially completely formaldehyde-free” means that the compositionsof the present invention are contaminated with, or liberate as a resultof curing, no more than about 0.25 percent by weight formaldehyde. Theterm “completely formaldehyde-free” means that the compositions of thepresent invention are contaminated with, or liberate as a result ofcuring, less than 5 parts per million (ppm) formaldehyde.

The term “snap cure” refers to the ability of the composition to curerapidly. For roll coating compositions “snap cure” means that thecomposition can cure to a substantially tack-free state in less thanabout one minute at 200 degrees C. More preferred compositions can cureto a substantially tack-free state in less than 30 seconds at 200degrees C.

The term “solvent” refers to a volatile liquid component of thecomposition that does not react during the curing or heating steps. Mostof the solvent is generally volatilized during a heating step and doesnot become incorporated into the cured coating.

The term “one-stage” means that all of the components are present in asingle “ready-to-use” formulation that is provided to a user.

The term “active hydrogen group” means a chemical functional group thatcan react under certain conditions with an acid, an anhydride, a saltthereof, or the like. In the context of the present invention, activehydrogen groups include alcohols, primary and secondary amines, thiols,and the like.

The term “active hydrogen group compound” means a chemical compound thatcontains one or more active hydrogen groups.

The term “extended epoxy resins” means an epoxy resin that has beenchain extended.

The term “quarternized epoxy resin” means an epoxy resin that hasundergone reaction with a tertiary amine. In this process, a tertiaryamine attacks one or more epoxide groups of the epoxy resin.

The term “polyacid” means a polymer (e.g., a homopolymer or co-polymer)that comprises a plurality of acidic functional groups. A polyacid maybe, for example, derived from ethylenically unsaturated acids ormixtures of ethylenically unsaturated acids and other monomers (e.g.,vinyl monomers).

The term “polyanhydride” means a polymer (e.g., a homopolymer orco-polymer) that comprises a plurality of anhydride functional groups. Apolyanhydride may be, for example, derived from ethylenicallyunsaturated anhydrides or mixtures of ethylenically unsaturatedanhydrides and other monomers (e.g., vinyl monomers).

The term “shelf-stable” means that compositions such as the one-stagecoating composition do not undergo degradation, crosslinking, or otherundesirable processes at standard temperatures and pressures forprolonged periods. Preferred compositions are shelf-stable for at leastone month, more preferred compositions are shelf-stable for at leastthree months, most preferred compositions are shelf-stable for at leastsix months, and optimally are shelf-stable for at least one year.

The term “vinyl monomer” refers to ethylenically unsaturated compoundsthat can react under conditions that form polymeric compounds.

DETAILED DESCRIPTION

The hardenable coating compositions of the present invention preferablyincorporate (i) a first compound having an acid number greater thanabout 100, and (ii) a second compound having two or more active hydrogengroups.

In one embodiment, the hardenable coating compositions of the presentinvention are useful for coating on substrates (e.g., the roll coatingof hardenable compositions on metal cans). The materials for thepreferred hardenable coating compositions include a

First compound (e.g., a polyacid) and a second compound (e.g., an activehydrogen group compound). Suitable materials are typically combined inliquid media (e.g., water or mixed solutions of water and water miscibleorganic liquids or emulsions). When combined in liquid media, thepolyacid and active hydrogen group compound of the preferred one-stagecoating compositions form flowable mixtures that can be shipped andstored at standard temperature and pressure without commerciallyunacceptable increases in coating viscosity or unsatisfactory changes incoating properties due to gellation or other degradative processes. Theyadditionally have drying and curing profiles that comport withproduction scale operations.

Preferably, the one-stage formulations form shelf-stable flowablemixtures in liquid media such as water or mixtures of water and watermiscible organic liquids. Also, they can be shipped and stored atstandard temperature and pressure without unacceptable increases inviscosity or unsatisfactory changes in properties (e.g., coatingproperties) due to gellation or other degradative processes.

The invention also relates to substrates that are coated with hardenablecoating compositions. The hardenable coating compositions may be appliedby conventional techniques to a wide variety of substrates (e.g., metal,plastic, wood, concrete, asphalt, etc.) in the form of sheets, strips orcoils. Metal coated substrates are especially useful in the packaging,processing, and holding of foods and beverages. In addition, thehardenable compositions of the invention may be used as a binder forproducts such as wood laminates and the like.

The coatings are typically applied on a substrate by a process such as,for example, lamination, solution or dispersion coating, spraying (e.g.,air or airless spraying, electrostatic spraying, etc.), roll coating,reverse roll coating, padding, saturating, dip coating or the like.Coating compositions can also be applied as a film by extrusion in meltform through an extrusion coating die onto a substrate.

After application to a substrate, the composition typically is thenhardened. In one embodiment, the composition is heated and dried toremove any optional solvents or carriers and cure the hardenablecomposition. Preferred hardenable coating compositions form hard solidswhen cured that protect the substrate (e.g., protect a metal can fromscratching or marring). The invention also relates to substrates thatare impregnated with hardenable compositions.

Suitable compositions of the present invention may be formulated havinga wide variety of solids content depending upon the application of thecomposition. Electro-coat compositions of the present invention mighthave a relatively low solids content (e.g., 10% or so), compositions forspray application might have a 20% or so solids content, while stillother compositions might have a 100% solids content. The preferredsolids content for a particular application can be selected by thoseskilled in the art. Typical roll coating composition of the presentinvention have a relatively high solids content. Preferred roll coatingcompositions (e.g., can exterior varnish coatings) will have from about20% to about 80%, more preferably from 30% to 70%, and most preferablyfrom 35% to 50% solids content, by weight.

Suitable first compounds of the present invention include linear orbranched polymers which possess pendant acid groups (or anhydride orsalt groups thereof) and which are sufficiently nonvolatile so that theywill remain available for reaction with the other starting materialsduring hardening (e.g., heating and drying) operations.

Suitable pendant acid groups for the present invention include sulfonicacid groups, phosphonic acid groups, carboxylic acid groups or the like.Preferred acid groups are carboxylic acid groups. Suitable pendantanhydride groups for the present invention include anhydrides of theaforementioned acid groups.

Suitable pendant salt groups include salts of the aforementioned acids,including sodium, lithium, potassium, magnesium, calcium, aluminum,ammonium, phosphonium and quaternary ammonium salts. Preferred saltsinclude sodium, lithium, potassium, ammonium, phosphonium and quaternaryammonium salts. If desired, a portion of the pendant acid groups may beconverted to the salt. For example, a portion of the pendant acid groupsmay be converted to a salt with an amine (e.g., excess amine that wasused to form a quaternized epoxy resin as discussed below).

Suitable first compounds of the present invention include polyacids,Polyanhydrides, salts thereof, or mixtures thereof having an acid numbergreater than About 100. Preferred compounds have an acid number in therange of from about 100 to 863, more preferably from about 200 to 700,and most preferably from about 250 to 600. The acid number as used inreference to the present compositions is the number of milligrams ofpotassium hydroxide required to neutralize one gram of the solidpolyacid polymer. The acid number of an anhydride-containing polymer isdetermined by initially hydrolyzing the anhydride-containing polymer toobtain the corresponding polyacid polymer. After drying, the acid numberis then determined in the same manner as for a polyacid polymer. Theacid number of a salt compound may be determined as the number for alike acid compound that has not been converted to the salt.

A high acid number is generally preferred. While not intending to bebound by theory, it is believed that the acid number should be highenough to facilitate the formation or reformation of a sufficient amountof anhydride during cure. Anhydride formation (which may beintermolecular but that is more likely intramolecular) is believed to bean integral part of the curing mechanism. Consequently, polyacids havinga low acid number are believed to be less efficient in the formation orreformation of anhydride (e.g., due to the greater separation betweenacid groups) and are thus less efficient in the curing process.

Preferred polyacid or polyanhydride polymers include homopolymers orcopolymers prepared from ethylenically unsaturated carboxylic acid orcarboxylic anhydride monomers and other optional monomers. The acid oranhydride monomers may be polymerized alone or with one or moreadditional vinyl monomers. Low molecular weight polymers are preferredfor certain applications as is discussed herein.

Ethylenically unsaturated acids and anhydrides suitable for the presentinvention include compounds having from about 3 to about 20 carbons, 1to 4 sites of unsaturation, and from 1 to 5 acid or anhydride groups orsalts thereof.

Non-limiting examples of useful ethylenically unsaturated acid monomersinclude acids such as, for example, acrylic acid, methacrylic acid,crotonic acid, fumaric acid, maleic acid, cinnamic acid, 2-methyl maleicacid, itaconic acid, 2-methyl itaconic acid, α,β-methyleneglutaric acid,and the like or mixtures thereof. Preferred unsaturated acid monomersinclude acrylic acid, methacrylic acid, crotonic acid, fulmaric acid,maleic acid, 2-methyl maleic acid, itaconic acid, 2-methyl itaconic acidand mixtures thereof. More preferred unsaturated acid monomers includeacrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleicacid, itaconic acid, and mixtures thereof. Most preferred unsaturatedacid monomers include acrylic acid, methacrylic acid, maleic acid,crotonic acid, and mixtures thereof.

Non-limiting examples of suitable ethylenically unsaturated anhydridemonomers include compounds derived from the above acids (e.g., as pureanhydride or mixtures of such). Preferred anhydrides include acrylicanhydride, methacrylic anhydride, and maleic anhydride.

Suitable co-monomers for polymerization with the ethylenicallyunsaturated carboxylic acid or an ethylenically unsaturated anhydridemonomers include vinyl monomers such as styrene, α-methyl styrene,acrylonitrile, methacrlonitrile, methyl acrylate, ethyl acrylate,ethylhexyl acrylate, n-butyl acrylate, hydroxyethyl acrylate,hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropylmethacrylate, isobutyl methacrylate, glycidyl methacrylate, vinyl methylether, vinyl acetate, and combinations. Preferred vinyl monomers arestyrene, α-methyl styrene, and ethylhexyl acrylate.

Suitable first compounds (e.g., polyacid or polyanhydride polymers)useful in practicing the present invention include polymers having awide variety of molecular weights, depending on the final useapplication of the composition. For coating applications the molecularweight should be selected such that the final composition has thedesired coating properties as well as the desired cured physicalproperties. For example, when the composition is used in a sprayapplication the molecular weight should be tailored to avoid veiling.When used in a roll coating operation the molecular weight should betailored to avoid misting and/or to optimize effective open time. Apreferred weight average molecular weight range for roll-coatingoperations is between about 500 and 20,000 Daltons. A more preferredweight average molecular weight range for roll-coating operations isbetween about 750 and 10,000 Daltons. A most preferred weight averagemolecular weight range for roll coating operations is between about1,000 and 5,000 Daltons.

Suitable hardenable compositions of the present invention also containat least one suitable second compound (e.g., an active hydrogen groupcompound). Preferred second compounds are believed to function ascrosslinking agents that react with the first compound under curing orhardening conditions.

If desired, the first compound and the second compound may be providedin a single combined compound. Such a combined compound would comprisefunctional moieties of both the first compound (e.g., pendant acidgroups, etc. as discussed above) and the second compound (e.g., activehydrogen groups as discussed below). For purposes of this application,the first and second compounds will be discussed as separate compounds.However, it is understood that a combined 1^(st)/2^(nd) compound mightbe employed as well.

Suitable second compounds useful as starting materials to prepare thehardenable compositions of the present invention include compounds (suchas, for example, alkylene, arylene, and/or arylalkylene compounds)containing at least two active hydrogen groups, such as hydroxy groups,primary or secondary amino groups, thiol groups, or combinationsthereof. More preferred second compounds are sufficiently nonvolatilethat they remain substantially available for reaction with the othercomponents of the composition during hardening (e.g., heating andcuring).

For certain applications, e.g., water-based roll coating compositions,preferred second compounds include water soluble polyols or polyamines.Di-functional compounds, tri-functional compounds, multi-functionalcompounds, or mixtures thereof may be used.

Suitable active hydrogen group compounds may be used alone or combinedwith one or more additional active hydrogen group compounds to achievehigher levels of crossliiking in the cured coating compositions.

Suitable active hydrogen group compounds include, but are notnecessarily limited to glycerol, ethylene glycol, propylene glycol,trimethylol propane, triethethylol ethane, ethylene diamine,ethanolamine, propanolamine, butanolamine, pentanol amine,diethanolamine, triethanolamine, pentaerythritol, sorbitol, sucrose,bisphenol A, quaternized epoxy resins, trihydroxyethyl isocyanurate,resorcinol, catechol, gallol, and various other polyols. The activehydrogen group compounds may also be addition polymers containing atleast two hydroxyl groups such as, for example, polyvinyl alcohol,partially hydrolyzed polyvinyl acetate, or homopolymers or copolymers ofhydroxyethyl methacrylate, hydroxypropyl methacrylate, and the like.

Although a variety of epoxy resins are useful for preparing the activehydrogen group compounds, the epoxy resins are preferably epoxy resinswith at least two epoxide groups. Suitable epoxy resins include glycidylethers or glycidyl esters of aromatic or alkylaromatic moieties.Suitable epoxy resins include aromatic polyethers based on the bisphenolstructure that contain terminal epoxide functionality and activehydrogen groups. Preferred epoxy resins have at least two terminalepoxide groups. Preferred epoxy resins are similarly functionalized andhave a number average molecular weight of up to 5,000 and an epoxyequivalent weight of up to 2,500. More preferred epoxy resins have anumber average molecular weight of about 1,000 to 5,000 and an epoxyequivalent weight of about 500 to 2,500. Most preferred epoxy resinshave a number average molecular weight of 2,000 to 4,000 and an epoxyequivalent weight of about 1,000 to 2,000. Commercially available epoxypolymers include EPON™ 828, 1001, 1004, 1007, 1009, 2004 resins,available from the Shell Chemical Co., Houston, Tex.

Active hydrogen compounds suitable for practicing the invention can beprepared from epoxy resins. In one embodiment, an epoxy resin and atertiary amine are reacted to provide a compound that has activehydrogen groups and quaternary amine groups. This reaction canconveniently be carried out at a temperature of about 70°-120° C.Alternatively, the epoxy resin may be reacted with the tertiary amine toform a resin having quaternary ammonium hydroxide groups that aresubsequently converted into quaternary ammonium acid salts throughreaction with the acid. The acids typically include polyacids,carboxylic acids, sulfonic acids, and/or phosphorus-based acids.

Suitable second compounds useful in practicing the present inventioninclude compounds having a wide variety of molecular weights, dependingon the final use application of the composition. For coatingapplications the molecular weight of the second compound should beselected such that the final composition has the desired coatingproperties as well as the desired cured physical properties. Forexample, when the composition is used in a spray application themolecular weight should be tailored to avoid veiling. When used in aroll coating operation the molecular weight should be tailored to avoidmisting and/or to optimize effective open time. A preferred weightaverage molecular weight of the second compound for roll-coatingoperations is less than about 20,000 Daltons. A more preferred weightaverage molecular weight range for roll-coating operations is betweenabout 100 and 20,000 Daltons. A most preferred weight average molecularweight range for roll coating operations is between about 200 and 10,000Daltons. An optimal weight average molecular weight range for rollcoating operations is between about 300 and 5,000 Daltons.

The hardenable compositions of the present invention may also includealong with the polyacid and the active hydrogen group compound, otheroptional additives. Suitable optional additives that may be incorporatedin the formulations include, for example, carriers (e.g., solvents),catalysts, stabilizers, initiators, photoinitiators, emulsifiers,pigments, fillers, anti-migration aids, curing agents, coalescents,wetting agents, biocides, plasticizers, crosslinkers, anti-foamingagents, colorants, waxes, anti-oxidants, viscosity modifiers, reactivediluents (e.g., ethoxylated bisphenol-A's such as SYN FAC 8009,FLO-MO-BIS, etc.), or combinations thereof.

In one embodiment, the compositions of the present invention contain anoptional carrier. The carrier may be used, for example, to facilitateapplication of the composition to the substrate. Preferred carriersinclude water and non-VOC (e.g., organic) carriers. These preferredcarriers might be used alone or with optional co-solvents.

Suitable preferred carriers include: water and non-VOC carriers. Anon-VOC carrier is a volatile compound that has a reaction rate with thehydroxyl radical and ultraviolet light (UV) that is faster than ethane.Suitable non-VOC carriers include: chlorobromomethane; 1-bromopropane;n-alkane (C12-C18); t-butyl acetate; perchloroethylene;benzotrifluoride; parachlobenzotrifluoride; acetone;1,2-dichloro-1,1,2-trifluoroethane; dimethoxymethane;1,1,1,2,2,3,3,4,4-nonafluoro-4-methoxy butane;2-(difluoromethoxymethyl)-1,1,1,2,3,3,3-heptafluoropropane;1-ethoxy-1,1,2,2,3,3,4,4,4-nonafluorobutane;2-ethoxydifluoromethyl)-1,1,1,2,3,3,3-heptafluoropropoane; methylenechloride; and mineral oils.

Other solvent carriers may be used as well in the compositions of thepresent invention. Preferred organic solvent carriers are typically madeup of saturated organic compounds having a molecular weight of less thanabout 300 such as lower alcohols, lower alkyl esters, cyclic esters,lower alkyl amides, cyclic amides, lower alkyl ethers, and mixturesthereof. Non-limiting examples include butyl cellosolve, diethyleneglycol diethyl ether, glycol dimethyl ether, ethoxy ethyl propionate,butyl carbitol, hexyl carbitol, hexyl cellosolve, butanol, amyl alcohol,propanol, propyl cellosolve, isopropanol, etc.

Preferred compositions have a volatile organic compound level of lessthan 0.25 kg/l of coating composition and solvent.

In one embodiment, the composition of the present invention contains anoptional catalyst. The catalyst may be used, for example, to facilitatecure of the composition.

Suitable catalysts include mineral acids (e.g., sulfuric, phosphonic,polyphosphonic, hydrochloric, hydrobromic, hydroiodic, HF, etc.,preferably phosphonic); nitric acid; esters of nitric acid; boric acid;esters of boric acid; organosulfonic acids (e.g., methyl sulfonic,p-toluene sulfonic, benzene sulfonic acid, napthylene sulfonic, etc.);organophosphonic; phosphoric acid organic esters (e.g., methyphosphonicacid, ethylphosphonic acid, etc.); and carboxylic acids (e.g., aceticacid, acrylic acid, benzoic acid, etc.). Preferred carboxylic acids havethe general formula R¹—COOH, where R¹ can be H or any alkyl or arylradical. Preferred sulfonic acids have the general formula R²—S(O₂)OH,where R² can be H or any alkyl or aryl radical. Preferred phosphonicacids have the general formula R³O—P(O)(OR⁴)(OR⁵), where R³, R⁴, and R⁵can be any combination of alkyl or aryl radical or H.

Preferred compositions for use in roll coating applications (e.g.,varnishes for can coating operations) are clear when wet. This allowsthe technicians to rapidly assess the printing operation in real time.Opaque or non-clear wet coatings can obscure the underlying printingthus causing delays in spotting underlying printing problems. Given thatmany can coating operations run at very high speed any delay spottingthe defect results in the waste of a large number of cans.

Suitable hardenable compositions of the invention for use as a rollcoating composition have a #4 Ford cup viscosity of about 40 to about 90seconds at 25° C. Preferred roll coating compositions have a #4 Ford cupviscosity of about 60 to about 85 seconds at 25° C. Most preferred rollcoating compositions have a #4 Ford cup viscosity of about 70 to about80 seconds at 25° C.

The compositions of the present invention are preferably formulated tobe shelf-stable one-stage compositions. This permits easy handling bythe end user. If desired, however, the composition may be provided in amulti-pack format. In such cases the end user would mix two or morecompositions together, e.g., immediately prior to use. Such compositionsmight have a shorter shelf life after being mixed than the separatecomponents had prior to mixing.

EXAMPLES

The foregoing disclosure provides all the parameters of the presentinvention. The following illustrative Examples further characterize theinvention but are not meant to provide general limitation thereof

Test Methods:

The following is an overview of the testing employed to determine theperformance of potential coating candidates.

Solution Viscosity:

Quantifies the flow rate of a liquid coating through the orifice of a #4sized Ford Cup. The measurement is quantified by determining the time(in seconds) the given volume of liquid coating requires to completelyflow through this orifice at 25° C. For roll coatings, a flow rate ofbetween 20 and 200 seconds is suitable. Preferably, the flow rate forroll coatings is between 30 and 150 seconds, more preferably between 40and 120 seconds, most preferably between 60 and 100 seconds, andoptimally between 40 and 90 seconds.

Non-Volatile Content:

Quantifies the percentage of a liquid coating that remains‘non-volatile’ after undergoing a given heating cycle. For this testing,a sample size of 0.5 g+/−0.02 g of liquid coating is used. This quantityof coating is essentially ‘flowed’ with 3.0 ml of deionized water, and abaking time of 60 minutes at 110° C. is used to remove volatilecomponents. For roll coatings, a non-volatile content of between 15 and100% by weight is suitable. Preferably, the non-volatile content of aroll coating is between 20 and 80%, more preferably between 30 and 60%,and most preferably between 35 and 42%.

Calculated VOC Content:

Quantifies the weight of ‘non-exempt’ volatile organic compounds thatare emitted from a gallon of liquid coating during the testing cycle asoutlined in the Non-Volatile Content test method described above.Determined values for coatings are expressed in lbs. of organicvolatiles per gallon of wet coating. For roll coatings, a maximum VOCcontent of 0.25 kg or less of volatile organic compounds per liter ofwet coating is most desirable. More preferred coatings have less than0.1 kg/l VOC, and most preferred coatings have less than 0.05 kg/l VOC.

Wet Solution Appearance:

Describes the appearance of a solution of wet coating in terms ofclarity, compatibility, etc., as determined by a qualitative visualanalysis. For roll coatings it is desirable for the wet coating to beclear and compatible (homogeneous).

Misting/Slinging:

Measures the resistance of a liquid coating to sling or spray away froma cylindrical application roll (e.g., as used in conventional rollcoating of liquid coatings) as it comes into contact with uncoatedaluminum beverage cans. A laboratory type tester suitable for performingthis assessment includes a miniature applicator roll (approximately 69mm diameter) attached to an electric motor, a separate free rotatingminiature roll holding an uncoated aluminum beverage can, and a sheet ofglass to collect any wet coating ejected from between the two rolls. Arotation speed of approximately 1000 rpms is determined to be theoptimal simulation of commercial application units for these sizedrolls. The misting performance is measured by coating the applicatorroll with wet coating, setting the roller speed for 1000 rpms, placingin contact with the second miniature roll holding the aluminum beveragecan, and measuring liquid coating collected on the sheet of glass over atime period of 20 seconds. The misting performance is qualitativelymeasured on a 0-10 scale, with a 10 meaning that none of the coating isejected after 20 seconds. The rating scale is summarized as follows: 0to 3=heavy undesirable misting (i.e., the glass collected coating overabout 30% or more of the surface); 4 to 6=moderate misting (i.e., theglass collected coating over about 11 to 29% of the surface); 7 to9=slight misting (i.e., the glass collected coating over about 2 to 10%of the surface); 10=no misting (i.e., the glass collected coating overless than about 1% of the surface), at 20 seconds. For roll coatings, amisting rating of 7 or greater is considered desirable.

Air Drying:

Measures the ability of a liquid coating, applied to yield a dry filmthickness of 2.2+/−0.63 g/m², to remain tacky at room temperature. Asdescribed in the tables, a coating is considered a PASS if it remainstacky for at least 15 minutes at room temperature and a FAIL if it istack free prior to the 15-minute mark. More preferred coatings remaintacky for at least 30 minutes, and most preferred coatings remain tackyfor at least one hour under these conditions.

Snap Cure:

Quantifies the rate at which a liquid coating applied at the desired dryfilm thickness, on an appropriate substrate, and baked (cured) at 200°C. will become tack free when exposed to a fabric capable of detectingtack on an organic film. Tack of a coating is measured at the 200° C.temperature. Test conditions for the optimized test include; a dry filmthickness of around 2.2+/−0.63 g/m², a sheet of end stock aluminum asthe substrate, and a red, cotton laboratory ‘rag’ as the fabric. A tackfree time of less than 30 seconds of curing time is the most desirablefor roll coatings. Any tack free times of less than 30 seconds areconsidered a PASS, while times over 30 seconds are considered a FAIL.

Pasteurization Blush/Adhesion:

Measures the ability of a cured coating composition to resistdiscoloration (blushing) and adhesion loss (from the given substrate)when exposed to a typical beverage pasteurization sequence in deionizedwater. For roll coatings, a water temperature of 82° C. and a soakingtime of 30 minutes is used. A roll coating is considered to PASS forblushing if no discoloration is observed following the pasteurizationsequence. Any discoloration results in a FAIL.

Following the pasteurization sequence, the adhesion of the coating isassessed using a crosshatch adhesion test (˜3.2 mm square pattern andstandard #610 tape (available from 3M Company)). The tape is applied tocrosshatched area and removed quickly at 90° from the substrate surface.A coating is said to display acceptable adhesion (considered a PASS) if100% of the substrate surface remains coated following thepasteurization sequence. A coating is given a rating of FAIL if at leastsome of the substrate surface is exposed (i.e., some of the coating isremoved) following the pasteurization sequence.

Solvent Resistance:

Measures the extent of resistance of a cured film towardsabrasion/dissolution to rubbing repeatedly back and forth with a clothsoaked in methyl ethyl ketone MEK). The solvent resistance is quantifiedby the number of double rubs (back and forth once) until a break in thecoating to the substrate has been established. For roll coatings an MEKresistance of at least 10 double rubs is desirable, preferred rollcoatings have an MEK resistance of at least 20 double rubs, morepreferred roll coatings have an MEK resistance of at least 40 doublerubs.

Dry Film Appearance:

Describes the appearance of a cured film in terms of clarity,smoothness, etc., as determined by a qualitative visual analysis. Forroll coatings, it is desired for the dried film to be clear, smooth, andglossy.

Example 1 Preparation of Polyacid Compounds

Run 1: Preparation of Polyacid Compound I

A reaction flask equipped with a stirrer, condenser tube, and inert gasinlet is charged with 57.2 g of diethylene glycol dimethyl either,(diglyme). A sparge of Nitrogen is begun, and some light agitation ofthe reaction flask initiated. The temperature of the flask is set for170° C. In a separate vessel, methacrylic acid, 132.5 g (1.54 mol),2-ethylhexyl acrylate, 66.2 g (0.36 mol), styrene, 22.1 g (0.21 mol),and dicumyl peroxide, 15.5 g (0.06 mol) is mixed. The mixture is gentlystirred until the dicumyl peroxide dissolves. Once the diglyme hasreached 170° C., the temperature set point is reduced to 162° C. Theaddition of the monomer/initiator mixture is started. Theinitiator/monomer mixture is added over a period of about 180 minutes.After the addition is complete, the temperature of the reaction flask ismaintained for an additional 120 minutes to complete the polymerizationprocess. A temperature range of 160-170° C. is maintained throughout thereaction time. Following the 120 minute holding time, the reaction flaskis set for 100° C. Once the reaction has cooled to 100° C., benzoylperoxide, 2.0 g (0.008 mol) is added. The reaction contents aremaintained at 100° C. for an additional 60 minutes. After the 60-minutehold time, the reaction flask is set for a temperature of 90° C. Amixture of dimethyl ethanolamine, 48.0 g (0.54 mol) and deionized water96.0 g is added to the reaction flask, over 10 minutes. The reactiontemperature is maintained at 90° C. for 60 minutes. Following this60-minute hold, the reaction flask is set for 80° C., and 331.0 g ofdeionized water is added, over a 60-minute period. Once the wateraddition is complete, the reaction flask is allowed to cool, undergentle agitation, to room temperature (˜25° C.). The polyacid compoundcan be discharged and characterized for solution/chemical properties.

The polyacid compound yielded the following characteristics:

Molecular Mass (MW) by Gel Permeation 2,630 Daltons ChromatographySolids Content (30 minutes at 160° C.) 34.3% by Weight Acid number(Titration with methanolic KOH) 346.0 mg KOH/gRun 2: Preparation of Polyacid Compound II

The polyacid was prepared according to the procedure of Ex. 1, Run 1,except diglyme is replaced with diethylene glycol diethyl ether (ethyldiglyme) as the solvent during polymerization.

Run 3: Preparation of Polyacid Compound III

The polyacid was prepared according to the procedure of Ex. 1, Run 1,except diglyme is replaced with Ektapro EEP as the solvent duringpolymerization.

Run 4: Preparation of Polyacid Compound IV

A monomer/initiator mixture is prepared by combining methacrylic acid,2360.0 g (27.4 mol), styrene, 1182.0 g (11.4 mol), ethyl acrylate, 394.0g (3.94 mol), benzoyl peroxide, 253.4 g (1.0 mol), and 34.6 g ofn-butanol. The mixture is gently mixed until all of the benzoyl peroxidehas dissolved. Ten percent, by weight, of this mixture, is added to areaction flask equipped with a stirrer, condenser tube, and inert gasinlet. In addition, 1632.6 g of n-butanol and 136.3 g of deionized wateris also added to the reaction flask. A sparge of Nitrogen is started,and light agitation of the reaction flask is initiated. The temperatureof the flask is set for 100° C. The remaining monomer/initiator premixis added uniformly over a period of 2.0 hours. A temperature of 100-110°C. is maintained throughout this time. Once all of the monomer/initiatorpremix has been added, the contents of the flask are maintained at100-110° C. for an additional 2.5 hours, to complete the polymerization.After the 2.5 hour holding time, 2685.2 g of n-butanol, 189.0 gdeionized water, and 1108.7 g 2-butoxy ethanol are added to the reactionflask. The contents of the reaction flask are allowed to cool to roomtemperature (˜25° C.). The polyacid compound can be discharged foranalysis.

The polyacid compound yielded the following characteristics:

Molecular Mass (MW) by Gel Permeation 17,500 Daltons ChromatographySolids Content (30 minutes at 160° C.) 39.6% by Weight Acid number(Titration with methanolic KOH) 381.0 mg KOH/gRun 5: Preparation of Polyacid Compound V

The polyacid was prepared according to the procedure of Ex. 1, Run 4,except that 2-butoxy ethanol is used in place of the n-butanol.

Run 6: Preparation of Polyacid Compound VI

The polyacid was prepared according to the procedure of Ex. 1, Run 5,except the monomer composition is (by weight) 60.0% methacrylic acid,35% 2-ethylhexyl acrylate, and 5% styrene.

Run 7: Preparation of Polyacid Compound VII

The polyacid was prepared according to the procedure of Ex. 1, Run 6,except about 90% of the 2-butoxy ethanol charge is replaced by asolution of 22% (by weight) of dimethyl ethanol amine in deionizedwater.

Run 8: Preparation of Polyacid Compound VIII

The polyacid was prepared according to the procedure of Ex. 1, Run 1,except the resulting polyacid compound is not diluted by addition ofdimethyl ethanolamine and deionized water.

Run 9: Preparation of Polyacid Compound IX

The polyacid was prepared according to the procedure of Ex. 1, Run 8,except the diglyme is replaced with ethyl diglyme.

Run 10: Preparation of Polyacid Compound X

A reaction flask equipped with a stirrer, condenser tube, and inert gasinlet is charged with 55.9 g of diethylene glycol dimethyl either,(diglyme). A sparge of Nitrogen is begun, and some light agitation ofthe reaction flask initiated. The temperature of the flask is set for170° C. In a separate vessel, methacrylic acid, 158.6 g (1.84 mol),2-ethylhexyl acrylate, 42.5 g (0.23 mol), styrene, 14.2 g (0.14 mol),and dicumyl peroxide, 15.5 g (0.06 mol) is mixed. The mixture is gentlystirred until the dicumyl peroxide dissolves. Once the diglyme hasreached 170° C., the temperature set point is reduced to 162° C. Theaddition of the monomer/initiator mixture is started. Theinitiator/monomer mixture is added over a period of about 180 minutes.After the addition is complete, the temperature of the reaction flask ismaintained for an additional 120 minutes to complete the polymerizationprocess. A temperature range of 160-170° C. is maintained throughout thereaction time. Following the 120 minute holding time, the reaction flaskis set for 100° C. Once the reaction has cooled to 100° C., benzoylperoxide, 2.0 g (0.008 mol) is added. The reaction contents aremaintained at 100° C. for an additional 60 minutes. After the 60-minutehold time, the reaction flask is cooled and discharged. The polyacidcompound can be discharged and characterized for solution/chemicalproperties.

The polyacid compound yielded the following characteristics:

Molecular Mass (MW) by Gel Permeation 2810 Daltons Chromatography SolidsContent (30 minutes at 160° C.) 83.4% by Weight Acid number (Titrationwith methanolic KOH) 425 mg KOH/g

Example 2 Preparation of Polyhydroxyl Compounds

Run 1: Preparation of Polyhydroxyl Compound I

A reaction flask equipped with a stirrer, condenser tube, and inert gasinlet is charged with 1000.0 g of diethylene glycol n-butyl ether,(butyl carbitol), and 440.0 g of dimethyl ethanolamine (4.94 equiv.).Gentle agitation is initiated to form a uniform solution of the amineand the solvent. Glacial acetic acid, 330.0 g (5.5 equiv.) is charged tothe reaction flask. The flask is set for a temperature of 55° C. In aseparate vessel, 645.0 g of butyl carbitol and 930.0 g of Epon 828 (4.9equiv.) epoxy resin is mixed. The mixture is gently stirred until thesolution of solvent and resin is homogeneous. The Epon 828 solution isslowly added to the reaction flask over a 60-minute period. Adequatecooling is provided to maintain the temperature of the reaction flask at<95° C. After the Epon 282 solution has been added, the reaction flaskis maintained 80° C. for 60 minutes. After the 60-minute hold iscomplete, the reaction flask is cooled to room temperature (˜25° C.).The resin solution can be discharged from the flask for analysis.

The Polyhydroxyl compound yielded the following characteristics:

Solids Content (60 minutes at 110° C.) 50.7% (by Weight) TheoreticalHydroxyl Number 7.1 mmol OH/g Residual Acid Value (titration with 31.0mg KOH/g methanolic KOH)Run 2: Preparation of Polyhydroxyl Compound II

The polyhydroxyl compound was prepared according to the procedure of Ex.2, Run 1, except the charge of the dimethyl ethanol amine is reduced by50% to 220.0 g.

The Polyhydroxyl compound yielded the following characteristics:

Solids Content (60 minutes at 110° C.) 47.5% (by Weight) TheoreticalHydroxyl Number 6.4 mmol OH/g Residual Acid Value (titration with 12.0mg KOH/g methanolic KOH)Run 3: Preparation of Polyhydroxyl Compound III

The polyhydroxyl compound was prepared according to the procedure of inEx. 2, Run 2, except the charge of butyl carbitol is replaced with butylcellosolve.

Run 4: Preparation of Polyhydroxyl Compound IV

The polyhydroxyl compound was prepared according to the procedure of Ex.2, Run 3, except 50% of the butyl cellosolve is replaced with deionizedwater.

Run 5: Preparation of Polyhydroxyl Compound V

A reaction flask equipped with a stirrer, condenser tube, and inert gasinlet is charged with Epon 828, 332.9 g (1.764 equiv.) and 50.0 g ofbutyl cellosolve. The mixture is gently agitated until it ishomogeneous. A sparging with nitrogen is initiated. Ethanolamine, 117.1g (3.84 equiv.) is added to the mixture. The mixture is allowed toexotherm to a maximum of 100° C. After the exotherm, the reactor ismaintained at 80° C. to complete the reaction. Deionized water, 142.9 g,is added to the flask to reduce the viscosity of the mixture. Thecontents of the reaction flask are cooled to room temperature (˜25° C.).The polyhydroxyl can be discharged for analysis.

The Polyhydroxyl compound yielded the following characteristics:

Solids Content (60 minutes at 110° C.) 59.7% (by Weight) TheoreticalHydroxyl Number 9.1 mmol OH/g

Example 3 In-situ Preparation of Polyhydroxyl Compound with a PolyacidCompound

446.9 g of the polyacid compound solution prepared in Ex. 1, Run 8 ischarged to a reaction flask equipped with a condenser, stirrer, andinert gas inlet. The contents are cooled to 100° C. and 111.2 g butylcarbitol, 158.4 g of Syn Fac 8009, and 170.7 g Epon 828 are added underlight agitation and mixed for 10 minutes until uniform. To this mixtureis added 104.7 g of dimethyl ethanolamine over a time period of 10-15minutes. The mixture is allowed to exotherm, and adequate cooling isprovided so that the exotherm temperature does not exceed 110° C. Themixture is held for a total of 30 minutes. Following the 30-minute holdtime, 967.5 g of deionized water is added to reduce the viscosity of theresin solution. The resulting solution was a clear, brownish solutionwith a solids content of 41.1% by weight (60 minutes at 110° C.).

Example 4 In-Situ Preparation of Polyhydroxyl Compound with a PolyacidCompound

The same components and reaction process were used as in Example 3,except the polyacid solution used was prepared as in Ex. 1, Run 9.

Example 5 Preparation of Polyacid Solution

A reaction flask equipped with a stirrer, condenser tube, and inert gasinlet is charged with 5166 g of deionized water. To the water is added3500 g of SMA XGA-10 flake resin (available from Elf Atochem) and 1334 gof dimethyl ethanolamine. The reaction components are maintained at 80°C. for 8 hours, until all of the SMA resin has been hydrolyzed anddissolved. The resulting resin is a clear, brownish solution with asolids content of 39.2% by weight (20 minute at 204° C.).

Comparative Example 6 General Description of Composition of ComparativeCoating 1

A sample of commercially available beer & beverage exterior varnish (#22Q02AA Two-piece Exterior Varnish (available from The ValsparCorporation, Minneapolis, Minn.)) was used as a “control” sample. Thiscoating has been determined to be commercially viable and is regarded asformaldehyde containing. This coating will herein be referred to asCoating 1 in the solution and film property evaluations.

Comparative Example 7 General Description of Composition of ComparativeCoating 2

A sample of an epoxy and acrylic based aqueous dispersion (# 10Q45AAtwo-piece water-based inside spray (available from The ValsparCorporation)) was used as a “control” sample. The sample is essentiallycomposed of an epoxy resin, and high molecular weight acrylic typeresins. This coating will herein be referred to as Coating 2 in thesolution and film property evaluations.

Example 8 Preferred Formaldehyde-Free Coatings

Several coatings were made by blending the following raw materials.

Coating 3 Coating 4 Coating 5 Raw Material Description (Parts) (Parts)(Parts) Example 1, Run 1 Polyacid 34.4 0.0 0.0 Compound I Example 2, Run2 Polyhydroxyl 15.6 0.0 0.0 Compound II Example 3 In-Situ Prepared  0.050.11 0.0 Polyacid/Polyol Example 4 In-Situ Prepared  0.0 0.0 50.11Polyacid/Polyol Example 5 Polyacid 28.2 28.43 28.4  Solution I 2-ButoxyEthanol Organic Solvent  0.0  3.38  3.38 Deionized Water VOC Compliant14.6 12.9  12.4  Solvent Additives Internal  7.2  5.18  5.71 lubricants,wetting aids, etc.

Example 9 Film Property Analysis of Various Coatings

The following coatings were evaluated using the previously describedtests.

Coating Sample: Coating 1 Coating 2 Coating 3 Coating 4 Coating 5Solution Viscosity 60 20 65 90 90 (seconds) Non-Volatile Content (%)37.1% 20.0% 41.3% 35.7% 36.6% Calculated VOC Content .19 .35 .24 .23 .25(kg/l) Wet Solution Clear Opaque Clear Clear Clear Appearance (visual)Compatible Compatible Compatible Compatible Compatible Misting/Slinging9-10 0-2 8-9 7-8 7-8 Air Drying PASS FAIL PASS PASS PASS Snap Cure¹ PASSPASS PASS PASS PASS Pasteurization Blush^(2,3) PASS PASS PASS PASS PASSPasteurization Adhesion^(2,3) PASS PASS PASS PASS PASS SolventResistance³ >50 20-30 >50 >50 >50 (MEK Double Rubs) Dry Film² ClearClear Clear Clear Clear Appearance (Visual) Smooth Smooth Smooth SmoothSmooth ¹30 seconds at 200° C. Cut-Off Criterion, End Stock Aluminum²Curing Conditions: Substrate: Commercially Available AluminumBeer/Beverage Cans; Curing Cycle: 45 seconds at 200° C., +2.5 minutes at200° C. ³30 minutes at 82° C. in deionized water

Example 10 In-situ Preparation of Polyhydroxyl Compound with a PolyacidCompound

286.3 g of the polyacid compound solution prepared in Ex. 1, Run 10 ischarged to a reaction flask equipped with a condenser, stirrer, andinert gas inlet. The contents are heated to 100° C. and 40.2 g of SynFac 8009, 113.2 g dimethyl ethanol amine, and 260 g deionized water areadded under light agitation and mixed for 30 minutes until uniform. Tothis mixture is added 58.4 g of EPON 828. The mixture is allowed toexotherm, and adequate cooling is provided so that the exothermtemperature does not exceed 115° C. The mixture is held for a total of5-10 minutes. Following the 5-10 minute hold time, 282.9 g of deionizedwater is added to reduce the viscosity of the resin solution. Theresulting solution was a clear, brownish solution with a solids contentof 41.1% by weight (60 minutes at 110° C.).

Having thus described the preferred embodiments of the presentinvention, those of skill in the art will readily appreciate that theteachings found herein may be applied to yet other embodiments withinthe scope of the claims hereto attached. The complete disclosure of allpatents, patent documents, and publications are incorporated herein byreference as if individually incorporated. Various modifications andalterations of this invention will become apparent to those skilled inthe art without departing from the scope and spirit of this invention.

1. A hardenable packaging coating composition, comprising: a polyacid compound comprising a homopolymer or a copolymer derived from a compound selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, crotonic acid, salts thereof and mixtures thereof, wherein the polyacid compound has a weight average molecular weight between about 750 and 10,000 Daltons and an acid number from 250 to 600; a polyhydroxyl compound, separate from the first compound, comprising a quaternized epoxy resin, wherein the polyhydroxyl compound has a weight average molecular weight between about 300 and 5,000 Daltons; and a liquid carrier, wherein the hardenable packaging coating composition is substantially formaldehyde free.
 2. A coating composition according to claim 1, wherein the polyacid compound is derived from methacrylic acid.
 3. A coating composition according to claim 1, wherein the polyacid compound has a weight average molecular weight of from about 1,000 to about 5,000 Daltons.
 4. A coating composition according to claim 1, further comprising a third compound having active hydrogen groups.
 5. A coating composition according to claim 4, wherein the third compound contains active hydrogen groups selected from the group consisting of hydroxyl groups, primary amino groups, secondary amino groups, thiol groups, and combinations thereof.
 6. A coating composition according to claim 4, wherein the third compound is selected from the group consisting of glycerol, ethylene glycol, propylene glycol, trimethylol propane, triethylolethane, ethylene diamine, ethanolamine, propanolamine, butanolanmine, pentanol amine, diethanolamine, triethanolamine, pentaerythritol, sorbitol, sucrose, bisphenol A, a quaternized epoxy resin, polyvinyl alcohol, trihydroxyethyl isocyanurate resorcinol, catechol, gallol, polymeric polyols, and mixtures thereof.
 7. A coating composition according to claim 1, wherein the composition has a solids content of from about 20% to about 80% by weight.
 8. A coating composition according to claim 1, which has a #4 Ford cup viscosity of about 40 to about 90 seconds at 25° C.
 9. A coating composition according to claim 1, which has no more than slight misting as determined with the misting/slinging test method.
 10. A coating composition according to claim 1, wherein the carrier comprises water.
 11. A coating composition according to claim 1, wherein the composition has a volatile organic compound level of less than 0.25 kg/l of coating composition and solvent.
 12. A coating composition according to claim 1, wherein the composition is in the form of an exterior varnish.
 13. A coating composition according to claim 1, wherein the composition remains tacky for at least 15 minutes at room temperature when applied to yield a dry film thickness of 2.2+/−0.63 g/m².
 14. The coating composition according to claim 1, wherein the quaternized epoxy resin is derived from an epoxy resin that comprises at least two epoxide groups.
 15. The coating composition according to claim 14, wherein the epoxide groups are terminal epoxide groups.
 16. A hardenable packaging coating composition, comprising: (a) a polyacid compound comprising a homopolymer or a copolymer derived from a compound selected from the group consisting of acrylic acid and methacrylic acid, salts thereof and mixtures thereof, wherein the polyacid compound has an acid number from 250 to 600 and a weight average molecular weight between about 750 and 10,000 Daltons; and (b) quaternized epoxy resin having a weight average molecular weight between about 300 and 5000 Daltons; and a liquid carrier comprising water, wherein the hardenable packaging coating composition has no more than slight misting as determined with the misting/slinging test method and can be rapidly cured to a substantially tack-free state in less than about one minute at 200° C., and wherein the coating composition is essentially formaldehyde free.
 17. A coating composition according to claim 16, wherein the first compound has a weight average molecular weight between about 1000 5000 Daltons. 